Mobile communication devices are in widespread use throughout the world, and in particular in metropolitan regions of the world. These devices have become so popular that in many places that it is often taken for granted that a person owns one. To remain competitive, manufactures of mobile communication devices and communication service providers have sought to include unique features to attract customers. One such feature is dispatch calling. Dispatch calling is similar in operation to direct two-way radio communication, sometimes referred to as “walkie-talkie,” or half duplex operation. However, modern dispatch calling utilizes a communication infrastructure to enable calling over large distances. Dispatch calling is initiated at a mobile communication device by pressing a so called push to talk (PTT) button, after selecting a party to call. Upon pushing the PTT button, the mobile communication device transmits a dispatch call request to a dispatch communication processor which sets up a dispatch call circuit with the intended target. Upon setting up the dispatch call circuit, the calling party receives an alert indicating the user may commence speaking. This happens in a manner that is much faster than normal duplex cellular telephony. The system is designed so that as soon as the user presses the PTT button they can begin talking, and their voice will be heard at the target device with very little delay. The target party does not need to answer the call as answering is automatic and the incoming voice signal is played over a loudspeaker of the receiving mobile communication device.
The speed with which other parties can be reached has made dispatch calling very popular in the marketplace. It is typically provided as an alternative calling mode on a mobile communication device which also has the ability to engage in more conventional cellular or interconnect telephony calling. The popularity of dispatch calling has led to multi-camp mobile communication devices, which have two (or more) radio frequency sections or modems so as to be camped on different communication systems at the same time, able to commence and receive calls from either of the systems while idle.
However, when the multi-camp mobile communication device is engaged in an interconnect call on one system, and receives a dispatch call on another system, the multi-camp mobile communication device conventionally has no way to respond because the audio section of the multi-camp mobile communication device is being used for the interconnect call. This leads to the dispatch calling party receiving a call failed result.